A Hydraulic Architecture Based on Multi-common Pressure Rail Principle Using Multi-chamber Cylinders for Excavators

Abstract This paper presents a hydraulic architecture based on the multi-common pressure rail (MPR) principle using multi-chamber cylinders for excavators and assesses the energy efficiency benefits for the case of a mid-size excavator. Among the different architectures that have been proposed to increase the efficiency of hydraulic systems in off-road vehicles, MPR systems have considerable advantages when multiple actuators exist and frequently operate under overrunning load conditions. Those systems also benefit from decoupling the primary units from the actuators so that both can operate with optimal efficiency. The use of multi-chamber cylinders further increases the flexibility to configure the connection between pressure rails and cylinder chambers for minimizing throttling losses. By trading off efficiency improvements and implementation costs, a hydraulic system using three-pressure rails with three-chamber cylinders is proposed. To confirm the efficiency gains and the controllability of the system, a full simulation model including the engine model, the hydraulic system model, and the machine dynamics model is presented for the case of a mid-size excavator. The compound controller consists of a velocity controller, a force index controller (FIC), a model predictive controller (MPC), and a flow allocator, which is designed and tuned for both linear actuators and rotary actuators, so that all primary actuators can be controlled by a MPR system with optimized efficiencies. The controller also adjusts the operating point of the internal combustion engine (ICE) along with the pump displacement controller, to let the ICE to always operate in a region of high efficiency with less partial loading. A case study for a 22-ton excavator is conducted with the developed simulation model and controllers. Considering typical truck loading and grading utilization cycles, simulation results show how the fuel consumption reduction can be up to 36% compared to the reference.